When a base waveform is applied to some devices in order to produce an output (the “forced,” or intended, response), such as a base waveform applied to a motor to produce a vibration, an “unforced” (or unintended) response may also be produced. In some cases, a canceling component may be applied to the device in order to reduce or eliminate the unforced response. However, reduction/elimination of the unforced response resulting from the application of a base waveform to a device may require a specific unforced response reduction/elimination canceling component. In order to utilize such an unforced response reduction/elimination canceling component to reduce/eliminate the unforced response, the particular unforced response reduction/elimination canceling component for the particular base waveform must be determined.
For example, a track pad device may be configured to provide a haptic response when touched by a user. To provide the haptic response, a base waveform may be applied to a motor or other actuator that vibrates to cause the track pad to move laterally on a gel bed or other moveable mounting mechanism. This lateral motion may be tactilely perceived by the user similar to a “click” of a button and may be indistinguishable to the user from a vertical motion.
However, the movement of the track pad may not strictly correspond to the base waveform applied to the motor or other actuator. Instead, after the base waveform is applied, the track pad may continue to move with decreasing amounts of kinetic energy for an amount of time after the initial movement associated with the base waveform until the track pad comes to a rest. This unforced response, or “ring down,” may be caused by the dissipation of the kinetic energy of the initial movement (similar to how a pendulum swings in increasingly smaller arcs after an initial force puts the pendulum in motion until coming to a stop) in conjunction with a restoring force or element that acts to return the track pad to its initial state, As a result of this unforced response, the haptic response provided by the track pad may feel imprecise or unpleasant to a user and, further, may differ from the intended haptic response. Additionally, the audible response that may result from the unforced response is even more likely to be unpleasant to a user.